include/linux/rcutiny.h

   1 /*
   2  * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, you can access it online at
  16  * http://www.gnu.org/licenses/gpl-2.0.html.
  17  *
  18  * Copyright IBM Corporation, 2008
  19  *
  20  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  21  *
  22  * For detailed explanation of Read-Copy Update mechanism see -
  23  *              Documentation/RCU
  24  */
  25 #ifndef __LINUX_TINY_H
  26 #define __LINUX_TINY_H
  27
  28 #include <linux/ktime.h>
  29
  30 struct rcu_dynticks;
  31 static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
  32 {
  33         return 0;
  34 }
  35
  36 /* Never flag non-existent other CPUs! */
  37 static inline bool rcu_eqs_special_set(int cpu) { return false; }
  38
  39 static inline unsigned long get_state_synchronize_rcu(void)
  40 {
  41         return 0;
  42 }
  43
  44 static inline void cond_synchronize_rcu(unsigned long oldstate)
  45 {
  46         might_sleep();
  47 }
  48
  49 static inline unsigned long get_state_synchronize_sched(void)
  50 {
  51         return 0;
  52 }
  53
  54 static inline void cond_synchronize_sched(unsigned long oldstate)
  55 {
  56         might_sleep();
  57 }
  58
  59 extern void rcu_barrier_bh(void);
  60 extern void rcu_barrier_sched(void);
  61
  62 static inline void synchronize_rcu_expedited(void)
  63 {
  64         synchronize_sched();    /* Only one CPU, so pretty fast anyway!!! */
  65 }
  66
  67 static inline void rcu_barrier(void)
  68 {
  69         rcu_barrier_sched();  /* Only one CPU, so only one list of callbacks! */
  70 }
  71
  72 static inline void synchronize_rcu_bh(void)
  73 {
  74         synchronize_sched();
  75 }
  76
  77 static inline void synchronize_rcu_bh_expedited(void)
  78 {
  79         synchronize_sched();
  80 }
  81
  82 static inline void synchronize_sched_expedited(void)
  83 {
  84         synchronize_sched();
  85 }
  86
  87 static inline void kfree_call_rcu(struct rcu_head *head,
  88                                   rcu_callback_t func)
  89 {
  90         call_rcu(head, func);
  91 }
  92
  93 #define rcu_note_context_switch(preempt) \
  94         do { \
  95                 rcu_sched_qs(); \
  96                 rcu_note_voluntary_context_switch_lite(current); \
  97         } while (0)
  98
  99 static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt)
 100 {
 101         *nextevt = KTIME_MAX;
 102         return 0;
 103 }
 104
 105 /*
 106  * Take advantage of the fact that there is only one CPU, which
 107  * allows us to ignore virtualization-based context switches.
 108  */
 109 static inline void rcu_virt_note_context_switch(int cpu) { }
 110 static inline void rcu_cpu_stall_reset(void) { }
 111 static inline void rcu_idle_enter(void) { }
 112 static inline void rcu_idle_exit(void) { }
 113 static inline void rcu_irq_enter(void) { }
 114 static inline bool rcu_irq_enter_disabled(void) { return false; }
 115 static inline void rcu_irq_exit_irqson(void) { }
 116 static inline void rcu_irq_enter_irqson(void) { }
 117 static inline void rcu_irq_exit(void) { }
 118 static inline void exit_rcu(void) { }
 119
 120 #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU)
 121 extern int rcu_scheduler_active __read_mostly;
 122 void rcu_scheduler_starting(void);
 123 #else /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) */
 124 static inline void rcu_scheduler_starting(void) { }
 125 #endif /* #else #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) */
 126 static inline void rcu_end_inkernel_boot(void) { }
 127 static inline bool rcu_is_watching(void) { return true; }
 128
 129 /* Avoid RCU read-side critical sections leaking across. */
 130 static inline void rcu_all_qs(void) { barrier(); }
 131
 132 /* RCUtree hotplug events */
 133 #define rcutree_prepare_cpu      NULL
 134 #define rcutree_online_cpu       NULL
 135 #define rcutree_offline_cpu      NULL
 136 #define rcutree_dead_cpu         NULL
 137 #define rcutree_dying_cpu        NULL
 138
 139 #endif /* __LINUX_RCUTINY_H */